1. Field of the Invention
The present invention relates to a vehicle generator control system for controlling the power generation of a generator driven by an internal combustion engine, and more specifically, to a vehicle generator control system which is capable of ensuring the excellent starting property of the engine as well as the stable operation of the engine immediately after the engine start-up.
2. Description of the Prior Art
There have been various techniques proposed, wherein the power generated by the generator is limited during cranking for starting the engine or immediately after the engine start-up when the engine is unstable, in order to improve the starting property of the engine and stabilize the rotation of the engine.
For example, Japanese First (unexamined) Utility Model Publication No. 59-157555 discloses a technique, wherein an alternator performs the power generation until the complete explosion or start-up of the engine (i.e., the state in which the engine is selfrotating or rotates independent of the starter); is detected, while the power generation is stopped for a given period of time after detection of the complete explosion. The power generated is and restarted thereafter so as to ensure the stable engine rotation immediately after the engine start-up.
Japanese First (unexamined) Patent Publication No. 6-261466 discloses a technique, which detects the termination of engine cranking based on the output voltage of a generator.
The exciting current to the generator is limited to a constant value for a given period of time so as to substantially stop the power generation of the generator, and then the exciting current to the generator is gradually increased. Because this technique, reduces the power generation load immediately after the engine start-up and subsequently increases the power generation load the stable engine rotation immediately after the engine start-up is ensured.
However, in the foregoing techniques, because the maximum exciting current is fed to the generator during engine cranking, the power generation torque required at that time causes a reduction in the cranking speed thereby comprising the engine starting property. Further, because the power generation is substantially stopped for a given time period after the completion of cranking and at a time where various electrical loads in the vehicle start to operate, there is a tendency for a shortage of power to occur.
In view of this, various techniques have been proposed wherein the power generation is stopped while the engine is under cranking.
For example, Japanese First (unexamined) Patent Publication No. 3-143300 discloses a technique wherein an alternator stops the power generation for a given time period after an ignition switch is operated to a starter drive position, so as to reduce a load applied to the engine.
Japanese First (unexamined) Patent Publication No. 3-173324 discloses a technique wherein exciting current to a generator is limited to a constant value so as to substantially stop the power generation immediately after starting the generator. After a lapse of time, the exciting current is then gradually increased to enhance the power generation, thereby shifting to the normal power generating operation.
However, unevenness in the time periods required for starting up the engine or stabilizing the engine rotation due to temperature conditions can not be dealt simply by stopping the power generation for the fixed time period as described above.
Because of this, other techniques have been proposed, that monitor actual engine operating conditions so as to control the power generation without relying on timers.
For example, Japanese First (unexamined) Patent Publication No. 61-171879 discloses a technique wherein a generator stops the power generation during engine cranking and starts the power generation when the termination of cranking is detected, based on the monitored engine speed.
Japanese First (unexamined) Utility Model Publication No. 59-189498 discloses another technique wherein the output of a generator is suppressed while the engine speed is not greater than idling speed.
However, in these techniques, the generator abruptly starts the power generation as the engine cranking is finished or the engine speed increases to exceed the idling speed, so that the corresponding load is abruptly applied to the engine. This tends to cause unstable engine rotation and, in some cases, engine stall.